DESC:
FIELD OF THE INVENTION
The invention relates to a high oxygen barrier and moisture resistance coating composition to be coated onto multi-layer polyolefinic film. The present invention further comprises of polyolefin film and a core layer of barrier composition coated/incorporated on to the outer polyolefin layer for preparation of laminates to be used for packaging of different grades of oil. The invention further relates to method of preparation of multi-layer polyolefin blown film with barrier composition coated/incorporated onto the outer polyolefin layer.

BACKGROUND OF THE INVENTION
Properties such as protection from oxygen and moisture are of great importance in oil packaging industry as are toughness and processability. Polyolefins particularly polyethylene films are characterized by toughness, excellent moisture and water vapour resistance but suffer from variable processability.

In order to meet the performance requirements of packaging a variety of oils, variety of composite films comprising of variety of polymers such as polyethylene, polypropylene etc have been used. In these composite films, the number of composite layers varies from one layer to multiple layers preferably five layers in order to meet the performance requirements of packaging different grades of oils.

US2019299574 is directed to a recyclable polyethylene multilayer structure providing oxygen barrier and comprising a first polyethylene layer as a first external layer, a second polyethylene layer as a second external layer and further comprises a layer made of a copolymer of ethylene and vinyl alcohol (EVOH) between the first external layer and the second external layer and a tie layer on each side of the EVOH layer and the tie layers comprise one or more copolymers of ethylene.

EP0801603 discloses a coated sheet material made by: (a) coating a porous substrate sheet with a barrier coating composition comprising a cross-linkable polymer resistant to penetration by water moisture, and a water-dispersible film-forming polymer that is resistant to penetration by grease and oil, said barrier coating composition forming a barrier layer on said substrate sheet material; and (b) coating said barrier layer with a release coating composition.

US20040106719A1 relates to a nanocomposite blend composition having superior barrier properties, and comprising a polyolefin resin and one or more nanocomposites having barrier properties, selected from an ethylene-vinyl alcohol (EVOH)/intercalated clay nanocomposite, a polyamide/intercalated clay nanocomposite, an ionomer/intercalated clay nanocomposite, and a polyvinyl alcohol (PVA)/intercalated clay nanocomposite; and a compatibilizer.

US6358576 relates to improved barrier coatings, to methods for coating substrates used in manufacturing food containers and to food containers having coatings which limit certain adverse effects of oxygen and/or moisture on the contents and discloses a layered composite containing a barrier layer comprising clay homogeneously dispersed in a continuous phase of polymeric material. The barrier layer is especially useful in the manufacture of liquid food containers.

WO2020086553 discloses Film structures including an A layer (i.e., outer skin layer), a B layer (i.e., a core layer), and C layer (i.e., an inner skin or sealant layer). The C layer is adjacent the first side of the B layer, and the A layer is adjacent the second side of the B layer. The B layer is positioned between the A layer and the C layer wherein the A layer includes high density polyethylene, the B layer includes linear low density polyethylene and a nucleating agent and the C layer includes one or more polymers.

WO2016034964 discloses three layer blown film structure and Grease resistant packaging prepared from a high density polyethylene (HDPE) composition that contains a nucleating agent and is included in an internal layer of a multilayer packaging structure and is prepared with a chromium or titanium (especially titanium) containing catalyst.

CN106147634 discloses a three-layer co-extruded blown film wherein the outer and middle layers of the film are made of low-density polyethylene LDPE, linear low-density polyethylene LLDPE and metallocene MLLDPE. It is prepared by mixing at a certain ratio. The bottom layer of the adhesive film is prepared by mixing low-density polyethylene LDPE and linear low-density polyethylene LLDPE at a certain ratio.

US8137774 discloses compositions comprising ethylene/vinyl acetate copolymers, tackifying resins and optionally polyolefins (for example, polyethylene and polypropylene) that provide strong, tight hermetic heat seals with an easily peelable opening feature to fluoropolymers such as polychlorotrifluoroethylene and also discloses multilayer structures and packages comprising these compositions wherein the multilayer polymeric sheet will involve at least three categorical layers including, but not limited to, an outermost structural or abuse layer, an inner barrier layer, bulking layer and/or adhesive layer, and an innermost layer making contact with and compatible with the intended contents of the package and capable of forming the necessary seals.

Though these barrier composites/films are likely to provide high performance and OTR rates, due to its high cost and complicated production processes are not conducive to be utilized for economical and efficient oil packaging.

The inventors of the present application have surprisingly noted that a small amount of inorganic or organic nano-crosslinking materials when applied in combination with polymeric alcohols to the outer layers of polyolefin substrate significantly improves oxygen barrier and moisture resistance property of the polyolefin substrate.

OBJECT OF THE INVENTION
According to one object, the present application provides a high oxygen barrier and moisture resistance coating composition to be coated onto multi-layer polyolefinic film

According to another object, the present application provides an efficient, economical and recyclable multi-layer polyolefinic film with high oxygen barrier (<10) and moisture resistance properties.

According to yet another object of the present application, there is provided a multi-layer film with a barrier composition coated/incorporated on to the outer polyolefin layer which is useful in the packaging of oil wherein the outermost and innermost/sealant layer is made of polyolefin and along with the barrier coating layer provides very low OTR (oxygen transmission rate).

According to yet another object of the present application, there is provided a multi-layer blown film which exhibits improved permeability to oxygen and moisture as well as possess toughness/swiftness and is easily processable.

According to yet another object of the present application, there is provided a multi-layer blown film with a coating which does not get distorted in the presence of oil.

According to yet another object, there is provided a coating composition comprising of polyvinylalcohol in combination with inorganic or organic micro/nano-crosslinking materials.

According to yet another object of the present application, there is provided a coating composition comprising of polyvinylalcohol in combination with inorganic or organic micro/nano-crosslinking materials coated/incorporated into the outer polyolefin layer.

According to yet another object of the present application there is provided a method for preparation of coating composition comprising of polyvinylalcohol in combination with inorganic or organic micro/nano-crosslinking materials.

According to yet another object of the present application, there is provided a polyolefinic film comprises of polyethylene (PE) layer or Polypropylene (PP) layer.

According to yet another object of the present application there is provided a method for preparation of multi-layer blown film comprising of Polyolefin layers and wherein the outer Polyolefin layer is coated/incorporated with barrier coating material comprising of water soluble polymeric alcohol in combination with inorganic or organic nano/ micro crosslinking materials.

According to yet another object of the present application there is provided a method for preparation of multi-layer blown film comprising of Polyolefin layers and wherein the outer Polyolefin layer is coated/incorporated with barrier coating material comprising of water soluble polymeric alcohol in combination with inorganic or organic nano/micro crosslinking materials.

According to yet another object of the present application there is provided a method for preparation of multi-layer blown film comprising of PE layers and wherein the outer PE layer is coated/incorporated with barrier coating material comprising of polyvinylalcohol in combination with inorganic or organic nano/micro-crosslinking materials.

According to yet another object of the present application there is provided a method for preparation of 3 layer blown film comprising of PE layers and wherein the outer PE layer is coated/incorporated with barrier coating material comprising of polyvinylalcohol in combination with inorganic or organic nano/micro -crosslinking materials.

SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a coating composition to be coated onto outer layer of the polyolefin based substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally a viscosity modifier.

According to another aspect of the present invention, there is provided a method for preparation of a coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution.
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition.

According to another aspect of the present invention, there is provided a high oxygen barrier and moisture resistance multi-layer polyolefin film comprising of a coating composition coated onto the outer layer of polyolefin substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent selected from water miscible organic solvents;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally comprising of a viscosity modifier.

According to another aspect of the present invention, there is provided a method for preparation of multi-layer polyolefin film with a coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution;
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition/solution
d. Spreading the coating solution of step (c) onto polyolefin based substrate to obtain multi-layer structure with a coating composition.

DETAILED DESCRIPTION OF THE INVENTION
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Few terms have been defined hereafter:

Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure. Definitions / full forms of few terms used throughout the specification are provided below:

OTR: Oxygen transmission rate, is method of measuring the oxygen gas permeability of the film or materials or laminate. This can be tested as per ASTM D3985.
WVTR: Water Vapour transmission rate, is method of measuring the moisture permeability of the film or materials or laminate. This can be tested as per ASTM F1249.
Micro/Nano inorganic crosslinking agent: Inorganic compound made of materials such as potassium, calcium, sodium salts etc., into clay compound with high aspect ratio & aggregates of platelets with very little surface area exposed or combination thereof and additionally the particle size distribution for nano crosslinking agent is in the range 50 nm to 100 nm and for micro crosslinking agent is in the range 100 nm to 10 mic m.
Micro/nano organic crosslinking agent: Organic compound made of materials such as lignin, hemicellulose, carboxy methyl cellulose, Arbo cellulose and nanocellulose etc into a compound with high aspect ratio & aggregates of fibers with very little surface area or combinations thereof, where the particle size distribution for nano crosslinking agent is in the range 50 nm to 200 nm and for micro crosslinking agent is in the range 100 nm to 10 mic m.

As used herein, the term Polyolefin refers to substances comprising of unsaturated bonds namely double bonds with repetitive units such as polyethylene, polypropylene etc and obtained via chain-growth polymerization from the monomer ethylene and propylene respectively.

As used herein, the term Polyolefin layer may include a laminate comprising plurality of films of polyethylene or polypropylene with varying thicknesses.

As used herein, the term oil includes animal and vegetable based fats and oils and mineral-derived oils and greases. The term is inclusive of fats and oils composed of triglycerides (esters of glycerol with fatty acids) and accompanying fatty substances, e.g., sterols of animal or plant origin, tocopherols, carotenoids, and phenolic compounds. The differentiation between fats (solid) and oils (liquids) are their physical states at room temperature. The physical properties are determined by the chain length and the number of cis-C=C double bonds in the fatty acid parts of the triglycerides. Longer chains and saturated fatty acids lead to higher melting points while shorter chains and unsaturated fatty acids result in lower melting points. Specific non-limiting examples of vegetable oils include sunflower, olive, coconut, palm, palm kernel, cottonseed, wheat germ, soybean, corn, safflower oil, hemp oil, canola/ rapeseed, avocado, and fully or partially hydrogenated vegetable oil / shortening. Specific non-limiting examples of animal fats include lard / pork / strutto, duck fat, and chicken, and tallow / beef. The present invention is not intended to include packages for dairy products such as milk, cream or butter. The use of linear low density polyethylene to prepare packaging for milk is well known.

Other oils include rosin, petroleum jelly, petroleum, soft paraffin/multi-hydrocarbon, hydrocarbon waxes / paraffin, wheel bearing grease, engine oil, asphalt, and petroleum grease.

The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

One of the key features of the present invention involves the usage of material comprising inorganic or organic nano-crosslinking materials in combination with polymeric alcohol which apparently is coated/incorporated into the outer polyolefin /PE/PP layer.

According to one embodiment, the present invention provides a composition to be coated onto outer layer of the polyolefin based substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally a viscosity modifier.

According to another embodiment the present invention provides a method for preparation of a coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution.
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition.

According to yet another embodiment, the present invention provides a high oxygen barrier and moisture resistance multi-layer polyolefin film comprising of a coating composition coated onto the outer layer of polyolefin substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent selected from water miscible organic solvents;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally comprising of a viscosity modifier.

According to yet another embodiment the present invention provides a method for preparation of multi-layer structure with a coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution;
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition/solution
d. Spreading the coating solution of step (c) onto polyolefin based substrate to obtain multi-layer structure with a coating composition.

According to yet another embodiment, the present invention comprises of a coating composition coated onto the outer layer of a polyolefin based substrate so as to form a barrier film and further layered with a laminated/printed polyolefin layer.

According to yet another embodiment, the present invention provides a coating composition for coating onto a polyolefin-based substrate wherein the coating composition comprises at least one water soluble alcohol based polymer and at least one inorganic (clay) or organic (cellulose) nano/micro-crosslinking agent and at least one drying agent.

According to yet another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one water soluble alcohol based polymer, wherein the at least one water soluble alcohol based polymer is PVOH with OTR of less than 10.

According to another embodiment the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one water soluble alcohol based polymer, wherein the at least one water soluble alcohol based polymer is BVOH with OTR of less than 10.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the a coating composition comprises a combination of at least one organic micro/nano-crosslinking agent and at least one inorganic micro/nano-crosslinking agent.

According to another embodiment the present invention provides a coating composition film for coating onto a polyolefin based substrate wherein the a coating composition film comprises a combination of at least one micro crosslinking agent or at least one nano crosslinking agent.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one organic micro/nano-crosslinking agent wherein the organic micro/nano-crosslinking agent is cellulose based.

According to another embodiment the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one organic nano-crosslinking agent such as nano-cellulose.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one organic micro-crosslinking agent such as micro cellulose.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition comprises at least one inorganic micro/nano-crosslinking agent wherein the inorganic micro/nano-crosslinking agent is clay based.

According to another embodiment the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composition film comprises at least one inorganic nano-crosslinking agent such as nano-clay.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the coating composite comprises at least one inorganic micro-crosslinking agent such as microclay.

According to another embodiment, the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the Polyolefin substrate is Polyethylene (PE) substrate.

According to another embodiment the present invention provides a coating composition for coating onto a polyolefin based substrate wherein the Polyolefin substrate is Polypropylene (PP) substrate.

According to another embodiment, the present application provides a method for preparation of coating material comprising of poly vinyl alcohol along with small amount of inorganic or organic nano-crosslinking materials comprising the steps of:
Step 1: Dissolve PVOH in hot water (preferably the temperature is >70°C) to obtain a solution.
Step 2: Add at least one micro/nano-crosslinking agent to solution of step 1 and homogenize for at least 2 hours at 500-2000 rpm;
Step 3: Take a polyolefin based film preferably PE based film and spread the coating solution of step 2 onto polyolefin based film to obtain desired final film with oxygen barrier capability.

According to another embodiment the present application provides a method for preparation of coating composition comprising of poly vinyl alcohol along with inorganic or organic micro/nano-crosslinking materials comprising the steps of:
Step 1: Dissolve PVOH in hot water (preferably the temperature is >70°C) to obtain a solution.
Step 2: Add at least one drying agent to the solution of step 2 to obtain a drying solution
Step 3: Add at least one micro/nano-crosslinking agent to drying solution of step 2 and homogenize for at least 2 hours at 500-2000 rpm;
Step 4: Take a polyolefin based film preferably PE based film and spread the coating solution of step 3 onto polyolefin based film to obtain desired final film with oxygen barrier capability.

According to another embodiment the present application provides a method for preparation of coating material comprising of poly vinyl alcohol along with inorganic or organic nano-crosslinking materials comprising the steps of:
Step 1: Dissolve PVOH in hot water (preferably the temperature is >70°C) to obtain a solution.
Step 2: Add at least one drying agent to the solution of step 2 to obtain a drying solution
Step 3: Add at least one micro/nano-crosslinking agent and at least one viscosity modifier to drying solution of step 2 and homogenize for at least 2 hours at 500-2000 rpm to obtain a coating solution
Step 4: Take a polyolefin based film preferably PE based film and spread the coating solution of step 3 onto polyolefin based film to obtain desired final film with oxygen barrier coating.

According to yet another embodiment, the present application provides a method for preparation of multi-layer blown film with a coating composition wherein the multi-layer film comprises of different polyolefin layered films.

The multi-layer blown film is a standard polyolefin film preferably polyethylene based film and may comprise of a single layered HDPE film or two layered film such as HDPE layered on an MDPE or an HDPE layered on a LDPE etc or a 3 layered film with HDPE + LDPE + LLDPE layering. Thus without limitation any polyolefin based film can be used as a substrate here.

According to yet another embodiment, the present application provides a method for preparation of multi-layer blown film comprising the steps of:
Step 1: Take the granules of HDPE polymer for preparation of outer layer
Step 2: Take the granules of LLDPE polymer for preparation of middle layer;
Step 3: Take the granules of LDPE polymer for preparation of inner layer;
Step 4: In a blown film 3 layer machine operable for a thickness of 30 micron – 100 micron, melt granules of step 1, Step 2 and step 3 separately and extrude these separately;
Step 5: Bring all the three extruded layers together, merge these and blow these to obtain single 3 layered blown film

According to yet another embodiment, the polyolefin substrate is selected from poly ethylene layer and polypropylene layer.

According to yet another embodiment, the polyolefin substrate (20mic to 200 mic) is selected from polyethylene material such as LDPE, MDPE, LLDPE or HDPE or polypropylene material such as Homopolymer PP, Terpolymer PP, Random Copolymer PP and Block Polymer PP.

According to yet another embodiment the polyolefin substrate comprises of a coating composition coated onto the outer layer of the polyolefin substrate and further layered with a laminated printed polyolefin layer.

The multi-layer blown film displays improved permeability to oxygen and moisture as well as possess toughness/swiftness and is easily processable.

The multi-layer film preferably 3-layer blown film employs barrier coating on the outermost polyolefin /PE/PP layer using water soluble polymeric alcohol such as PVOH, in combination with micro/nanocomposite such as cellulose and clay. This barrier coating composition is in particular characterized by high strength, excellent moisture and water vapour resistance. More specifically the present invention relates to multi-layer blown film with barrier coating which does not get distorted in the presence of oil and hence serves as effective medium for packaging of oil.

The purpose of the present invention is to provide an efficient, economical and recyclable multi-layer blown composite film preferably three-layer blown composite film with high oxygen barrier (<10 cc/sq.m/day at 23 deg C, 0% RH tested as per ASTM D3985) and moisture resistance for oil packaging thereby overcoming problems associated with prior art. Non-limiting examples of such oil products include Oils used in food applications, Motor oil, greases and Lubricants

According to yet another embodiment, the present application provides a three-layer blown film comprising of polyolefin /Polyethylene (PE)/ Polypropylene (PP) layers wherein the outer polyolefin /PE/PP layer of the three-layer blown film is coated/incorporated with a material comprising of water soluble polymeric alcohols such as poly vinyl alcohol along with inorganic or organic nano-crosslinking materials.

According to another embodiment, the material composition to be coated onto the outer polyolefin /PE layer comprises of:
a. polymeric alcohol such as poly vinyl alcohol (wherein the crystalline polymer is carrying a vinyl group)
b. at least one drying agent (organic solvents miscible with water)
c. at least one micro/nano-crosslinking agent (Nanomaterial which has the ability to form a torturous path)

The composition may also additionally comprise of at least one viscosity modifier such as PEG.

This material is added by making a coating on the outer layer of the substrate

In one of the embodiments, this invention includes a flexible laminate containing multiple layers of polyolefin /PE/PP polymer wherein the outer layer of the laminate (polyolefin /PE/PP layer) is coated with or incorporated through coating with material comprising inorganic or organic micro/nano-crosslinking materials in combination with polymeric alcohol, thereby significantly improving the OTR and providing high oxygen barrier properties.

A method for improving OTR of polyolefinic film laminate to be used for oil packaging, said method comprising Coating/incorporating material comprising inorganic or organic micro/nano-crosslinking materials in combination with polymeric alcohol onto the outer layer of the filament comprising the steps of:
a) Raw material is Polyolefinic material;
b) Film Making – Conversion of Polyolefinic materials into the film through a process like Blown film, cast film, Biaxial orientation process, Machine direction orientation process and film casting process etc.,
c) Printing or barrier coating – Coating or printing through on the polyolefin substrates through the process such as direct or reverse gravure, flexo, semiflexo etc.,
d) Barrier coating or printing - Coating or printing through on the polyolefin substrates through the process such as direct or reverse gravure, flexo, semiflexo etc.,
e) Lamination – Combining 2 or more substrates through a process such as dry or wet lamination or extrusion or Hot melt lamination process etc.,
f) Slitting – Reducing the wider width into smaller width which are required as per the packing lines.

Polyvinyl alcohol (PVA) is used in the concentration of 1 to 20% of the material to be incorporated /coated onto the outer polyolefin /PE layer.

The drying agent is selected from water miscible organic solvents such as alcohols selected from methanol, ethanol, propanol, Isopropyl alcohol Polyethylene glycol.

The at least one viscosity modifier that may be used in the present invention is selected from the group comprising glycerol, glycol and combinations thereof wherein the glycol can be polyethylene Glycol or propylene glycol having molecular weight in the range of 100 to 5000 daltons.

The drying agent is used in the concentration of 1 to 20% in the total coating composition weight to be incorporated onto the outer polyolefin /PE layer.

According to yet another object of the present application, there is provided a multi-layer blown film with a barrier composition coated/incorporated on to the outer polyolefin layer which is useful in the packaging of oil wherein the outermost and innermost/sealant layer is made of polyolefin and along with the barrier coating layer provides very low OTR (oxygen transmission rate).

According to yet another object of the present application, the muti layer polyolefin film would have coating composition weight ranging from 0.2 gsm to 5 gsm to achieve the barrier level depend on the substrate combinations.

According to another embodiment, the polyolefin substrate of the present application coated with barrier coating composition exhibits Oxygen barrier of < 10 CC/sq.m/day at 23 deg C/0% relative humidity. The Oxygen barrier of the polyolefinic substrate have been tested as per ASTM D 3985.

According to another embodiment, the polyolefin substrate of the present application coated with barrier coating composition exhibits moisture barrier of < 5 g/sq.m/day at 38deg C/90% relative humidity. The Moisture barrier of the polyolefinic substrate have been tested as per ASTM F1249.

The Cross-linker molecules used in the present application are able to form tortuous path in z-direction in the film and are selected from organic/inorganic Micro/Nanomaterials, such as cellulose, & clay. On application of uniform coating over the polyolefin substrate, the over all coating composition leads to crosslinking of coatings and such crosslinked coating will lead to formation of highly structured torturous path as shown in Figure.1

Description of Figures:
Figure 1: Torturous path formed due to coating of barrier composition of the present application

The concentration of cross-linking molecules/agents used in the present application is in the range of 0.001 to 10% weight of the coating composition to be incorporated /coated onto the outer polyolefin /PE/PP layer.

The Inventors observed that coating composition comprising of Poly vinyl alcohol (PVOH)/ Butyl Vinyl alcohol (BVOH) with crosslinking agents were able to form high torturous path on the substrate whereas EVOH is ethylene vinyl alcohol with clay will not have a very high torturous path, hence low barrier.

The non-limiting examples of the present application are provided hereinafter:

Working example: WE
Example 1: Lower limit of micro/nano cross-linking agent;
Example 2: High concentration of PVOH/BVOH;
Example 3: Higher limit of micro/nano cross linking agent;
Example 4: Lower concentration of PVOH.

S.No. Ingredient WE 1 Wt% Example2 Wt% Example 3 Wt% Example 4 Wt%
1 Substrate 3 layer film/ Laminate 2 layer film/ Laminate 2 layer film/
Laminate 3 layer film/
Laminate
2 Nanocellulose 0.001 ----- ----- -----
3 PVOH/BVOH 5 20 8 5
4 Nanoclay ----- 1 ----- 0.02
5 IPA 10 ----- ----- 4
6 PEG 400 2 1 2 20
7 Microcellulose ----- ----- 8 -----
8 OTR <5 <5 <5 <5
* OTR was measured using ASTM D 3985.

Method of preparation
Step 1: Dissolve PVOH in hot water (temp is 80°C) to obtain a solution.
Step 2: Add IPA to the solution of step 2 to obtain a drying solution
Step 3: Add nanocellulose to drying solution of step 2 and homogenize for at least 2 hours at 2000 - 2500 rpm to obtain a coating solution
Step 4: Take a 3 layered PE based film and spread the coating solution of step 3 onto 3 layered PE based film to obtain desired final film with oxygen barrier capability.

Non-working examples:
NWE 1: Micro/Nano cross linking agent not available
NWE 2: PVOH is absent
NWE 3: PVOH is lower than desired range
NWE4: Micro/Nano cross linking agent lower than desired range

S.No. Ingredient NWE1 Wt% NWE 2Wt% NWE 3Wt% NWE 4Wt% NWE 5 Wt% NWE 6 Wt%
Substrate 3 layer film 2 layer film Single layer film 3 layer film 3 layer film 3 layer film
1 Nanocellulose ----- ----- ----- ----- 15 0.1
2 PVOH 5 ----- 2 2 5 25
3 Nanoclay ----- 1 ----- 0.0005 ----- -----
4 IPA 10 ----- ----- ----- 5 5
5 PEG ----- 7 ----- ----- 7 7
6 Microcellulose ----- ----- 8 ----- ----- 0.1
OTR >500 >2000 <5 >200 Not commercialize able >2000

From the non-working examples, as provided above, it is observed that:
? when the barrier composition does not comprise of crosslinker then the OTR > 100.
? when the barrier composition does not comprise of drying agent than the Speed of coating (<10 m/min) while with drying agent the speed of coating >100m/min.
? when the barrier composition does not comprise of drying agent, then shrinkage issues pertaining to film dimensional stability is observed.
? when the barrier composition does not comprise of water soluble polymeric alcohol such as PVOH, then Film formation will not occur.
? when the barrier composition does not comprise of Viscosity modifier, no coating uniformity is observed.

The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art and the principles applied herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
,CLAIMS:
1. A coating composition to be coated onto outer polyolefin layer of the polyolefin-based substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally comprising a viscosity modifier.

2. A coating composition as claimed in claim 1 wherein the polymeric alcohol is used in the concentration of 1 to 20% of the weight of coating composition to be incorporated /coated onto the outer polyolefin layer.

3. A coating composition as claimed in claim 1 wherein the polymeric alcohol is selected from the group consisting of PVOH (poly vinyl alcohol) and BVOH (butene-diol vinyl alcohol copolymer).

4. A coating composition as claimed in claim 1 wherein the drying agent is used in the concentration of 1 to 20% of the weight of coating composition to be incorporated /coated onto the outer polyolefin.

5. A coating composition as claimed in claim 1 wherein the drying agent is a water miscible organic solvent.

6. A coating composition as claimed in claim 5 wherein the water miscible organic solvent is alcohol based solvent selected from methanol, ethanol, propanol, Isopropyl alcohol and glycol.

7. A coating composition as claimed in claim 1 wherein the nano/micro crosslinking agent is selected from nano-cellulose, micro-cellulose, nano-clay and micro-clay.

8. A coating composition as claimed in claim 1 wherein the nano/micro crosslinking agent is present in the range of 0.001 to 10% of the coating composition to be incorporated /coated onto the outer polyolefin layer.

9. A coating composition as claimed in claim 1 wherein the optional viscosity modifier is selected from glycerol, glycol and combinations thereof.

10. A coating composition as claimed in claim 9 wherein the glycol can be polyethylene Glycol or propylene glycol having molecular weight in the range of 100 to 5000 daltons.

11. A method for preparation of coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution;
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition.

12. A high oxygen barrier and moisture resistance multi-layer polyolefin film comprising of a coating composition coated onto the outer layer of polyolefin substrate wherein the coating composition comprises of:
a. water soluble polymeric alcohol;
b. at least one drying agent selected from water miscible organic solvents;
c. at least one crosslinking agent selected from nano/micro crosslinking agent and
d. optionally comprising of viscosity modifier.

13. A multi-layer polyolefin film as claimed in claim 12 wherein the polyolefin substrate is polyethylene film or polypropylene film with one or more layers.

14. A multi-layer polyolefin film as claimed in claim 13 wherein the polyolefin substrate with a thickness of 20 mic to 200 mic is selected from polyethylene material such as LDPE, MDPE, LLDPE or HDPE or polypropylene material such as Homopolymer PP, Terpolymer PP, Random Copolymer PP and Block Polymer PP.

15. A multi-layer polyolefin film as claimed in claim 12-14 wherein the polyolefin substrate coated with barrier coating composition exhibits Oxygen barrier of < 10 CC/sq.m/day at 23 deg C/0% relative humidity.

16. A multi-layer polyolefin film as claimed in claim 12-14 wherein the polyolefin substrate coated with barrier coating composition exhibits moisture barrier of < 5 g/sq.m/day at 38deg C/90% relative humidity.

17. A method for preparation of multi-layer polyolefin film with a coating composition comprising the steps of:
a. Dissolve water soluble polymeric alcohol in hot water to obtain a solution;
b. Adding at least one drying agent to the solution of step (a) to obtain a drying solution;
c. Adding at least one micro/nano-crosslinking agent to the drying solution of step (b) and homogenize for at least 2 hours at 500 – 2000 rpm to obtain a coating composition/solution
d. Spreading the coating solution of step (c) onto polyolefin based substrate to obtain multi-layer structure with a coating composition.